1. Field of the Invention
The present invention relates to clock pulse generators and in particular to high accuracy startable pulse train generators.
2. Description of the Prior Art
Precise interval measurements are essential in nuclear and ballistic time-of-flight tests, radar ranging and in the characterization of active components, such as integrated circuits. In making such interval measurements, utilization of a pulse train, startable and stopable on command, of short duration pulses with accurately controlled interpulse spacing is desirable for use with digital signal processing equipment. For a detailed discussion of time interval measurements, reference is made to "Measure time interval precisely," by David Martin, Electronic Design, 24 Nov. 22, 1974, pp. 162 et seq.
Three terminal transferred electron devices, hereinafter termed Transferred Electron Logic Devices (TELD), having an anode, cathode and gate terminals, are well known. Such devices are more commonly known as Schottky-Barrier-Gate Gunn-Effect Digital-Devices. The general operation of a TELD may be described as follows.
Upon a voltage difference between the anode and gate terminals exceeding a predetermined threshold value a mobile "dipole" domain is created in the TELD. A dipole domain comprises an electron charge depletion region preceding an electron charge accumulation region. The dipole domain travels from the cathode to the anode of the device, causing a drop in the current through the device during the transit period. Thus, in response to the voltage difference between the anode and gate exceeding the threshold value, the TELD, in cooperation with an impedance loading the cathode, generates a negative polarity voltage pulse having pulsewidth determined primarily by the geometry of the device. The above-mentioned anode-gate difference voltage threshold value is determined by the anode and gate bias voltages with respect to the cathode, and the TELD geometry and material parameters. For a more detailed description of TELD's reference is made to "Threshold Condition of Schottky Gate-Gunn Pulse Device" Y. Utsugi et al., Review of the Electrical Communication Laboratories, Vol. 23, Nos. 3-4, March-April 1975, p. 279 et seq.
TELD's have been utilized as high speed pulse repeaters, that is, pulse train generators. For a discussion of prior art high speed pulse repeaters, reference is made to "Characteristics and Applications of a Schottky-Barrier Gate Gunn-Effect Digital-Device" by Sugeta et al., IEEE Transactions on Electron Devices, Vol. ED-21, No. 8, Aug. 1974, pp. 504 et seq. Such prior art pulse repeaters operate with pulsed, as opposed to D.C., biasing. Pulse biased repeaters are not suitable for time interval measurement since inherent time delays in the pulse bias supply introduce large errors into time measurements. Moreover, such prior art pulse train generators require a TELD having both short pulse generation capability and an extremely sensitive gate triggering characteristic. By "sensitive gate triggering characteristic" it is meant that the TELD must trigger into operation in response to a low magnitude gate-pulse. TELD's having both the abovementioned characteristics are very difficult to construct in accordance with present technology.